1. Field of the Invention
A pressurized incineration method for disposing of solid waste material while simultaneously producing electrical and thermal energy.
2. Description of the Prior Art
Power systems that generate electricity by driving gas turbines or steam turbines, using solid waste material as fuel, have existed for some time. Gas turbine power systems which operate on solid fuel are designed as either indirect-fired or direct-fired systems. These systems have several main components, an air compressor, a furnace or combustor chamber, a power turbine, and an electrical generator. The electrical generator and air compressor are driven by energy from the turbine, created by expansion of hot compressed air through the turbine. Hot compressed air for expansion in the turbine is developed by compressing air in the compressor and heating the compressed air with thermal energy created by the furnace or combustor.
In indirect-fired systems, the furnace or combustor typically operates as a separate functional unit apart from a functional unit containing the air compressor and the power turbine which are combined as integral parts of a gas turbine. This design for indirect-firing protects the gas turbine power section from corrosive effluents and particulate matter typically present in the hot exhaust gases from a furnace or combustor operating on solid fuel by use of a high temperature heat exchanger. Gas turbines generally do not work well when directly exposed to pressurized gases containing corrosive effluents and particulates because of wear and abrasion caused by such elements to the turbine's power section. The furnace/combustor unit and the compressor/turbine unit (gas turbine) exchange heat by means of a heat exchanger wherein ducts containing compressed air flowing to the power turbine are placed in close proximity to ducts bearing highly heated exhaust gases from the furnace or combustor, resulting in exchange of heat from the hot exhaust gases to the compressed air. This heated and compressed air then drives the power section of the gas turbine which in turn drives the turbine air compressor and an electric generator. Woodward U.S. Pat. No. 2,401,285 and Fernandes U.S. Pat. No. 3,473,331 disclose incinerator systems akin to that described above.
In direct-fired systems, the solid fuel is burned in an pressurized combustor and the heated products of combustion are vented directly into the power section of the turbine. The combustor is part of an integral pressurized unit including both the compressor and the power section of the gas turbine. In many instances, gas cleaning equipment may be employed between the combustor and the power section of the gas turbine. One example of a direct-fired gas turbine is disclosed in U.S. Pat. No. 4,850,288.
The general design of power systems incorporating a steam turbine is designated as the Rankine Cycle. In Rankine Cycle systems, a conventional boiler is used to create steam which drives a steam turbine. These systems may be designed to operate on a variety of fuels, including traditional hydrocarbon fuels and various other types of solid fuel. This type of power system is prevalent in the public utility industry and used to generate the majority of the electrical power in the U.S.
Some systems designed to produce energy, not to incinerate waste, use a diesel engine directly coupled to an electrical generator. The main pressurized exhaust stream is expanded across a turbocharger unit which provides energy to compress air for the diesel engine. The diesel engine is contained in the same functional unit as the power recovery turbine and turbocharger, so that the pressurized gaseous exhaust from the engine is fed directly through the turbocharger and the separate power recovery turbine. The mechanical energy created by expanding the remainder of the diesel exhaust across an additional turbine is transformed into additional electrical energy by an electrical generator. These systems are generally designed to operate on hydrocarbon gases or liquids. Their basic function is to generate either mechanical or electrical energy, not to eliminate solid waste material.